Method of and apparatus for reproducing a colored image by electrophotographic means

ABSTRACT

AN ELECTROPHOTOGRAPHIC RECORDING ELEMENT IS EXPOSED WITH THREE DIFFERENTLY COLORED AND DIFFERENTLY ORIENTED BANDED IMAGES IN REGISTER. THE RESULTANT BANDED LATENT IMAGE OF EACH OF THE COLOR-BANDED IMAGES IS DEVELOPED SELECTIVELY WITH A DIFFERENT TONER OF A COMPLEMENTARY COLOR FOR A SUBTRACIVE PROCESS. THE NOVEL APPARATUS COMPRISES DICHROIC REFLECTORS AND THREE DIFFERENTLY ORIENTED LINE SCREENS FOR SIMULTANEOUSLY PROJECTING THREE ILLUMINATION PATTERNS OF THE COLORED IMAGE TO BE REPRODUCED WITH LIGHTS OF THREE PRIMARY COLORS. AT LEAST TWO ROTATABLE SCREW-TYPE TONER APPLICATORS ARE PROVIDED FOR DEVELOPING THE BANDS TO TWO OF THE COLOR-BANDED IMAGES THAT SLANT IN DIFFERENT DIRECTIONS.

June 6, 1972 055 3,667,841

MH'IHOD OE REPRODUCING A COLORDD .[M OGRAPHIC MEANS l5 Sheets-Sheet 1 AND APPARATUS FOR AGE BY ELECTROPHOT Filed March 26, 1970 R. 0 Y mm M WE W T N. T [A A M m m 0 0 Y B D. A. ROSS June 6, 1972 3,667,841

MI'Z'I'HUI) 0P ANI) APPARATUS FOR REPRODUCING A COLORED IMAGE ml ELECTROPHOTOGRAPHIC MEANS Filed March 20, 1970 3 Sheets-Sheet 2 Fig. 9a.

4 INVENTOR Donald A. Ross WVJW ATTORNEY June 6, 1972 D. A. ROSS 3,667,841

METHOD OF AND APPARATUS FOR REPRODUCING A COLORED IMAGE BY ELECTROPHOTOGRAPI'IIC MEANS Filed larch 26, 1970 3 Sheets-Sheet 3 RED GREEN BLUE IIO H4 l N VEN TOR Donald A. Ross haw/VE- %ww' ATTORNEY United States Patent 01 lice 3,667,841 Patented June 6, 1972 US. Cl. 355--4 Claims ABSTRACT OF THE DISCLOSURE An electrophotographic recording element is exposed with three differently colored and differently oriented banded images in register. The resultant banded latent image of each of the color-banded images is developed selectively with a different toner of a complementary color for a subtractive process. The novel apparatus comprises dichroic reflectors and three differently oriented line screens for simultaneously projecting three illumination patterns of the colored image to be reproduced with lights of three primary colors. At least two rotatable screw-type toner applicators are provided for developing the bands of two of the color-banded images that slant in different directions.

BACKGROUND OF THE INVENTION This invention relates generally to a method of and apparatus for reproducing a colored image by electrophotographic means, and more particularly to a method of and apparatus for reproducing a colored image on an electrophotographic recording element. The invention also relates to the reproduced colored image.

It has been proposed to produce full color reproductions electrophotographically by a microdispersion exposure system, using only a single exposure and a single development operation. In this prior-art system a prism is employed to disperse line segments of an original image into spectra which form a color-banded image of the original color image to be reproduced. The resulting color reproduction of this system is an image with parallel color bands that should blend to form a full color image. The parallel colored bands, however, are not as faithful to the colors of the original image as would be true if the colors were physically blended. Hence, steps are taken to diffuse the parallel color bands laterally, and unless this cross-diffusion is carried out, the resulting colored reproduction leaves much to be desired. Also, because all of the color bands in the colored reproduction are substantially parallel, an imperfect cross-diffusion operation may cause the colored reproduction to have an undesirable moire effect.

The novel method and apparatus of the present invention minimize the necessity for the cross-diffusion operation and provide an improved colored reproduction relatively free of moire patterns.

SUMMARY OF THE INVENTION The novel method of reproducing a colored image on an electrophotographic recording element is carried out by the novel apparatus wherein means are provided to expose the recording element with three banded images in superimposed register to form a latent image. Each banded image is in a different color and has its hands slanted in a different direction from that of the other banded images. Each band defines an exposure band on the recording element, and means are provided to develop the latent image on the exposure band selectively with a different toner in a complementary color for a subtractive process.

The novel colored image comprises at least two sets of colored parallel bands of toner superimposed over each other on a recording element. The bands of toner in each set are of a different complementary color for a subtractive process and are disposed at different angles with respect to the bands of toner in the other sets.

By the term exposure band is meant an elongated area on the recording element that either is, or can be, exposed by one of the bands in a banded image.

As used herein, the term complementary colors for a subtractive process means cyan (minus red), magenta (minus green), and yellow (minus blue).

BRIEF DESCRIPTION OF THE DRAWINGS FIG. =1 is a simplified diagrammatic illustration of a preferred embodiment of the novel apparatus for carrying out the novel method;

*FIGS. 2, 3 and 4 are fragmentary drawings of three diffrent line screens used in the apparatus illustrated in PI FIGS. 5, 6 and 7 are fragmentary drawings of toner applicators used in the apparatus illustrated in FIG. 1;

FIG. 8 is a drawing of a colored image to be reproduced by the apparatus illustrated in FIG. 1, portions of tile drawing being shaded for the colors red, green, and

FIG. 9 is a simplified diagram for illustrating the novel method of development of a recording element exposed by the colored image of FIG. 8;

FIG. 9a is a diagram illustrating the slant of exposure bands defined by color-banded images formed in the novel method; and

FIG. 10 is a simplified schematic diagram of another embodiment of apparatus for carrying out the novel method.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1 of the drawings, there is shown a preferred embodiment of novel apparatus 10 for reproducing a colored image, as from a photographic color transparency 12, on the surface 14 of an electrophotographic recording element 16.

The apparatus 10 comprises means to expose the recording element 16, when electrostatically charged, with three banded images, in superimposed register, each banded image being in a different primary color and each having parallel bands that slant in a different direction. To this end, a light source 11 projects an illumination pattern of the colored image of the color transparency 12 through a lens system, illustrated herein by a lens 18, and through a crossed-dichroic reflector system 20'.

The crossed-dichroic reflector system 20 has the property of reflecting lights of predetermined colors in different directions, and, at the same time, of transmitting without substantial modification lights of other colors. The construction and operation of dichroic reflectors are described in the following U.S. patents to Glenn L. Dimmick: 2,379,790, granted July 3, 1945, entitled Dichroic Reflectors; and 2,412,496, granted Dec. 10, 1946, entitled Color Selective Reflector. The crossed-dichroic reflector system 20 is described in detail in US. Pat. No. 2,672,502, issued to J. E. Albright on Mar. 16, 1954, for Color- Selective Optical System. Essentially, the crossed-dichroic reflector system 20 comprises filter means wherein red and blue lights are reflected in opposite direction, respectively, and green light is transmitted directly.

In operation, red light derived from the illumination pattern of the color transparency 12, is reflected by a dichroic reflector 22 of the system 20, and blue and green lights are transmitted without substantial modification.

Blue light, derived from the illumination pattern of the transparency 12, is reflected by the dichroic reflector 24 of the system 20, and red and green lights are transmitted without substantial modification. Green light, derived from the illumination pattern of the color transparency 12, is transmitted without substantial modification through both of the reflectors 22 and 24. Thus, the illumination pattern of the color transparency 12 is separated into three illumination patterns in the three primary colors red, green, and blue, respectively.

Means are provided to convert the three colored illumination patterns into three banded images, respectively, each having parallel bands that slant in a direction different from the direction of slant of the bands in the other banded images. To this end, an opaque line screen 26 is disposed in the optical path 28 of the green illumination pattern. The line screen 26, illustrated in FIGS. 1 and 2, comprises a sheet 29 of transparent material, such as glass or plastic material, with opaque parallel lines 30 (FIG. 2) ruled or painted thereon. A suitable line screen 26 is one wherein the number of opaque lines 30 is about 100 per inch and wherein the width of each opaque line 30 is substantially the same as the Width of the light-transparent bands 32 between the opaque lines. The lines 30 in the line screen 26 may be said to form an angle of with a reference line, such as, for example, a side (vertical) edge 34 of the line screen 26.

The optical path 36 of the red illumination pattern of the color transparency 12, reflected from the dichroic reflector 22, is caused to pass through an opaque line screen 38, and the optical path 40 of the blue illumination pattern, reflected from the dichroic reflector 24 is caused to pass through an opaque line screen 42. The number and thickness of lines and spacings in the line screens 38 and 42 are substantially similar to those in the line screen 26 with the exception that the lines 44 (FIG. 4) of the line screen 38 slant in a direction of -45 with respect to the lines 30 of the line screen 26, and the lines 46 (FIG. 3) of the line screen 42 slant in a direction that forms an angle of +45 with the direction of the lines 30 of the line screen 26.

The green banded image is transmitted along the optical path 28 directly through a cross-dichroic reflector system 50, similar to the system 20, and through an optical system, illustrated by a lens 52, onto the surface '14 of the recording element 16 at an exposure station 53. The red banded image is transmitted along the optical path 36 which is reflected by mirrors 54 and 56 onto a red dichroie reflector 58, of the system 50, through the lens 52 and onto the surface 14 of the recording element '16 at the exposure station 53. In a similar manner, the blue banded image is transmitted along the optical path 40 which is reflected by mirrors 60 and 62 onto a blue dichroic reflector 64, of the system 50, through the lens 52, and onto the surface 14 of the recording element 16 at the exposure station 53. The mirrors 54, 56, 60, and 62, the dichroic reflectors 58 and 64 of the system 50, and the lens system 52 are disposed so as to superirnpose, in register at the exposure station 53', the three green, red, and blue banded images on the surface 14 of the recording element 16 to expose the latter. The color banded images define exposure bands on the recording element 16. While the three primary colored images are superimposed on the surface 14, it is important to note, however, that the parallel exposure bands defined by each of the color-banded images slant in a different direction from the parallel exposure bands defined by the other color banded images (i.e. -45, 0, and +45) with respect to a reference line, such as a vertical or horizontal line.

The number of lines in the line screens and the directions of slant of these lines are not critical, and are given merely as illustrative examples.

The electrophotographic recording element 16 comprises a web of a relatively conductive substrate 66, such as paper or aluminum foil, coated with a photoconductive layer 68, such as photoconductive zinc oxide dispersed in 7 a resin binder. The recording element 16 may be dyesensitized to render it pancromatic to light in the visible spectrum.

The recording element 16 may be electrostatically charged by any means known in the art. For example, double corona discharge devices 70 and 72 are disposed on opposite sides, respectively, of the recording element 16 and are connected to a suitable source of unidirectional voltage (about 6 kv., not shown). The corona discharge device 70 is connected to the negative terminal of the voltage source and the corona discharge device 72 is connected to the positive terminal of the voltage source so that the surface 14 of the recording element 16 is charged uniformly negatively at a charging station 69. When the uniformly charged recording element 16 is exposed by the three color-banded images at the exposure station 53, in register, the exposed portion of the recording element 16 is selectively discharged in accordance with the intensity of light impinging upon it to form an electrostatic latent image. The web of the recording element 16 is adapted to be moved past the exposure station 53 and around a roller 74, in directions of the arrows 71 and 73, by any suitable means including a motor 75 coupled to the roller 74.

After it is exposed, the recording element 16 is moved past a developing station 76 where the resultant electrostatic latent image is developed selectively with electroscopic toners in complementary colors for a substractive process, as will be explained hereinafter in detail.

The developing means of the apparatus 10 comprise three developer troughs 80, 82, and '84 filled with magenta, yellow, and cyan electroscopic developer toners 86, 88, and 90, respectively. These toners may be either in a ferromagnetic dry mixture or they may be suspended in an inert insulating carrier liquid for application to the recording element 16 in a manner well known in the art. The particles of the colored toner may be electrostatically positive or negative, depending upon whether a direct reproduction or a reversal reproduction, respectively, of the image to be copied is desired.

A rotatable disc-type toner applicator 92, illustrated in detail in FIG. 5, is disposed with the trough 86 for applying magenta toner on discrete portions on the surface 14 of the recording element 16. The toner applicator 92 comprises a plurality of parallel discs 94 each having a width at its periphery substantially equal to that of a light-transmitting band 32 of the line screen 34 (FIG. 2). The discs 94 of the applicator 92 are spaced apart a distance equal to the width of a line 30 of the line screen 26.

Rotatable screw-type toner applicators 96 and 98 are disposed within the troughs 88 and for applying yellow electroscopic toner and cyan electroscopic toner, respectively, to selected discrete portions of the exposed surface 14 of the recording element 16, in a manner to be hereinafter explained. The toner applicators 92, 96, and 98 are disposed with their axes parallel to each other and are coupled to a motor 100 for rotation thereby. The toner applicators 92, '96, and 98 may also be coupled to each other for synchronous rotation.

The toner applicator 96, shown in FIG. 6, is in the form of a square-thread screw, the width of the peripheral screw (applicator) surface 102 is substantially equal to the width of an exposure band formed by a light-transmitting band of the line screen 42. The square-thread screw of the toner applicator 96 has a pitch of 45 and is adapted to be rotated in the direction of an arrow 104.

The toner applicator 98, shown also in FIG. 7, is substantially the same as the toner applicator 96, but its square threads slant in an opposite direction to those of the toner applicator 96. The square-thread screw of the toner applicator 98 has a pitch of 45. If the toner applicator 96 is considered a right-hand screw, then the toner applicator 98 is a left-hand screw. The toner applicator 98 is adapted to be rotated in a direction indicated by an arrow 106. If the toner applicators 92, 96, and 98 are to apply toners from a ferromagnetic electroscopic developer mixture, the toner applicators are made of magnetic material.

The novel method of reproducing a colored image on an electrophotographic recording element 16 will be described with reference to the novel apparatus 10. Let it be assumed that the transparency 12 is a colored slide with an image of the three primary colors: red, green, and blue in squares 110, 112, and 114, respectively, as shown in FIG. 8, and it is desired to reproduce this image on the recording element 16. The slants of the line-shadings of the squares 110, 112, and 114 represent the colors red, green, and blue. The recording element is first charged uniformly, in the dark, by the double corona discharge devices 70 and 72 at the charging station 69, and then moved to the exposure station 53 where it is exposed with red, green, and blue banded images in superimposed register, as described supra. The development of the resulting electrostatic latent image to produce a colored reproduction of the transparency 12 v(FIG. 8) will be explained with the reference to FIG. 9.

Referring now to FIG. 9, there is shown a diagrammatic representation of three sets of parallel exposure bands, designated R, G, and B, superimposed in register over each other, each set slanting in a different direction, as designated by arrows R, G, and B in FIG. 9a. The bands R, G, and B are the exposure bands defined by the color-banded images in the three primary colors produced by the illumination patterns projected through the line screens 38, 26, and 42, respectively, as explained supra. In developing the electrostatic latent image, resulting from the exposure by superimposed banded images in the three complementary colors, cyan toner is applied to the exposure bands R, magenta toner is applied to the exposure bands B, and yellow toner is applied to the exposure bands B, these toners being in complementary colors for a subtractive process. Electrostatically positive toners are used on a negatively charged electrophotographic recording element to provide a direct reproduction, as herein described. The applied toners may be fixed on the recording element 16 by a heater, shown in FIG. 1.

As is illustrated in FIG. 9, a large square 110a which represents a portion of the electrostatic latent image produced by the red square 110 of the transparency 12 (FIG. 9a) attracts developer material only in the unilluminated exposure bands G and B; that is, the bands which would have been illuminated by green or blue, it a green or blue image had been in the particular area 110 of the original color transparency 12. These latter unilluminated exposure bands being unexposed still carry an attracting electrostatic charge. The illuminated exposure bands R are heavily exposed and are completely discharged so that no developer material is attracted in those bands. Hence, the square 110a is developed with a combination of magenta and yellow toners, represented by shaded portions in FIG. 9. The magenta toner is applied by the disctype roller applicator 92 along parallel exposure bands G in the direction indicated by the arrows M, and the yellow toner is applied with the screw-type toner applicator 96 along the parallel exposure bands B in the direction indicated by the arrows Y. The magenta and yellow toners are applied to those portions (exposure bands G and B) of the square 110a Where they are attracted by an electrostatic charge. An advantage of the novel apparatus and method is that because the magenta and yellow toners are applied in different directions, they overlap each other in those areas where they are attracted by the same electrostatic charge and, hence, blend with each other to produce the color red. The development of the electrostatic latent image by the novel method obviates the necessity of cross-blending the toned image and tends to prevent moire effects.

The large square 112a ('FIG. 9) which represents a portion of the electrostatic latent image produced by the exposure of the banded green image (of square 112) is developed by cyan and yellow toners, each being applied in the direction of the arrows indicated by C and Y, respectively. The cyan and yellow toners are applied to their appropriate exposure bands R and B by rotating the screw-type toner applicators 98 and 96 about their axes because the pitch of their square-thread screws are matched to the slant of the lines of the line screens 38 and 42, respectively. The speed of movement of the recording element 16 and the rotation of the toner applicators are synchronized so that the toner applicators track their respective exposure bands. Thus, the cyan toner is applied in a direction of -45 with respect to the direction of the magenta toner, and the yellow toner is applied in a direction of +45 with respect to the direction of the application of the magenta toner. Since the green square 112 of the transparency 12 (FIG. 8) completely exposed the recording element 16 with green bands, they discharged the recording element thereat, and no toner is attracted to the resulting exposure bands G. The square 112a is, therefore, developed with cyan and magenta toners which, in combination, blend to produce green.

The square 114a, representing the banded electrostatic latent image resulting from the exposure by the square 114 of the color transparency 12, is developed with cyan and magenta toners in the directions indicated by the arrows C and M by roller applicators 98 and 92, respectively. Since the square 114a was exposed by blue bands, no toner is attracted in the exposure bands B because the recording element 16 was electrostatically discharged completely thereat. The combination of cyan and magenta toners, however, produces a blue color. If portions of the color transparency 12 (FIG. 8) contained colors other than red, green, and blue, that is, a combination of one or more of these colors, they would be separated into the primary colors red, green, and blue by the crossed-dichroic reflector system 20 and developed by those complementary colors that would be conventionally applied in a subtractive process to provide a colored reproduction.

Referring now to FIG. 10, there is shown another embodiment of apparatus for reproducing a colored image of the color transparency 12 on the recording element 16 in accordance with the novel method. The components of the apparatus 120 in FIG. 10 that are similar to those of the preferred apparatus 10 in FIG. 1 are designated by the same reference numbers. While the preferred apparatus 10 provides means for exposing the recording element 16 simultaneously with three differently colored and differently band-slant oriented banded images, the apparatus 120 provides means for exposing the recording element sequentially with the three differently colored and differently band-slant oriented banded images.

Referring now to FIG. 10, the surface 14 of the recording element 16 is illustrated as disposed to receive an exposure of a banded color image whose color is provided by a filter 122. An illumination pattern of the color transparency 12 is projected by the light source 11 through the lens system 18, the filter 122, which may be green, for example, and a line screen 26, for example, to produce a green banded image at the exposure station 53. If the filter 122 is red and the line screen is line screen 38, a red banded image is produced at the exposure station 53. If the filter 122 is blue and the line screen 42 is used, a blue banded image is produced at the exposure station 53. By exposing the negatively charged surface 14 of the recording element 16 sequentially to the green, red, and blue banded images, in register, a resultant electrostatic latent image is formed at the exposure station which can be developed by the novel method, as described in connection with FIG. 9, using the same development means illustrated in FIG. 1.

Although the means for exposing a recording element in accordance with the novel method and apparatus have been illustrated with a recording element that is electrostatically charged, the novel apparatus and method may also be employed with some recording elements without the necessity of charging them electrostatically. Some photoconductive layers, including those of zinc oxide, of recording elements, when exposed to light retain an increased state of conductivity for relatively long periods after the light has been turned off. Thus, when such a recording element is exposed to an illumination pattern, a conductivity latent image is formed such that the image areas have a greater electrical conductivity than the unexposed or background areas. Such recording elements and means for developing them are described in US. Pats. 3,010,883 and 3,010,884, both issued to E. G. Johnson and B. W. Neher on Nov. 28, 1961. The novel method and apparatus, as described, for example, with reference to FIG. 1, are suitable for developing conductivity latent images if the toners 86, 88, and 90 are of the liquid type, and a suitable bias voltage (not shown) is applied between the roller applicators 92, 96, and 98 and the conductive substrate 66 of the recording element 16.

Thus, there has been described a novel method of reproducing a color image on an electrophotographic recording element wherein the recording element is exposed either simultaneously or sequentially with three differently colored and differently band-slant oriented banded images, in superimposed register. Because the three colored toners used for developing the resultant latent image are applied to the exposure bands in different directions, toners that cross each other blend with each other, minimize the production of moire patterns, and obviate the necessity for a cross-diffusion operation on the toners.

The novel method and apparatus may also be used to reproduce a colored image from a colored negative transparency, instead of a colored positive transparency as explained supra. The only change necessary would be the use of cyan, magenta, and yellow toners with an opposite charge polarity to those used for making the direct colored reproductions. Cyan, magenta, and yellow toners of the same (positive) charge polarity may be used for making a reversal print as for making a direct print if the recording element is charged positive (instead of negative as described for the positive pirnt, supra). The recording element 16 may be charged positive by first charging it negative and then reversing the polarity of the corona discharge so as to charge the recording element positive. This latter method of providing a positive charge on the recording element is described in US. Pat. 3,412,242, issued to E. C. Giaimo, Jr. on Nov. 19, 1968, for Method of Charging a Zinc Oxide Photoconductive Layer with a Positive Charge.

What is claimed is: 1. In a method of reproducing a colored image on an electrophotographie recording element, the improvement comprising:

exposing said recording element simultaneously with three sets of differently colored and differently bandslant oriented banded images, in a single exposure of said colored image to be produced, in superimposed register, whereby to define thereon three sets of differently slanted exposure bands comprising a latent image of said colored image to be reproduced, and

developing the exposure bands defined by each set of said banded images selectively with electroscopic toner in a complementary color for a subtractive process, said developing being performed by a different toner applicator for each complementary color at substantially the same time during one relative motion between said recording element and the toner applicators.

2. In a method of reproducing a colored image as described in claim 1, wherein said exposing said recording element comprises projecting an illumination pattern of said colored image separately with each of three primary colored lights and through a different line-slant oriented opaque line screen for each colored light, whereby to produce said three differently colored and differently band-slanted banded images in register on said recording element. 3. In a method of reproducing a colored image on an electrophotographic recording element, the improvement comprising:

exposing said recording element with three differently colored and differently band-slant oriented banded images of said colored image to be produced, in superimposed register, whereby to define thereon exposure bands comprising a latent image of said colored image to be reproduced, developing the exposure bands defined by each of said banded images selectively with electroscopic toner in a complementary color for a subtractive process,

said exposing said recording element comprising projecting an illumination pattern of said colored image separately with each of three primary colored lights and through a different line-slant oriented opaque line screen for each colored light, whereby to produce said three differently colored and differently band-slanted banded images in register on said recording element, and

said projecting an illumination pattern of said colored image separately with each of three primary colored lights and through a different line-slant oriented opaque line screen for each colored light being performed simultaneously.

4. In a method of reproducing a colored image as described in claim 2, wherein said projecting an illumination pattern of said colored image separately with each of three primary colored lights comprises projecting said illumination pattern separately with red, green, and blue lights through separate line screens, said line screens being disposed to project, onto said recording element, the bands of one of said handed images at an angle of 45 with respect to the bands of a second of said banded images, and to project the bands of a third of said banded images at an angle of +45 with respect to the bands of said second banded image.

5. In a method of reproducing a colored image as described in claim 4, 'wherein said developing comprises moving, relative to said recording element, one toner applicator with cyan toner along the exposure bands defined by the banded image projected by said red light, a second toner applicator with magenta toner along the exposure bands defined by the banded image projected by said green light, and a third toner applicator with yellow toner along the exposure bands defined by the banded image projected by said blue light.

6. In a method of reproducing a colored image as described in claim 5, wherein said developing the exposure bands in two of said color banded images comprises applying two electroscopic toners with two rotatable screw-type applicators, re spectively, the thread of each screw tracking the exposure bands only in a respective color banded im age.

7. In apparatus for reproducing a colored image on an electrophotographic recording element, the improvement comprising:

means for exposing said recording element with three banded images in superimposed register, each banded image being in a different primary color and each having its bands slanted in a different direction with respect to the direction of slant of the bands in the other of said banded images, whereby to define exposure bands on said recording element, comprising a latent image of said colored image to be reproduced, means for developing the exposure bands defined by each of said three banded images selectively with separated by light-transmitting bands, the width of each of said lines being equal to the width of said light-transmitting bands. 10. In apparatus for reproducing a colored image as described in claim 7, wherein said means for developing the exposure bands comprises at least one rotatable toner applicator with a and said means for projecting an illumination pattern of said colored image separately with each of three pril0 mary colored lights comprises dichroic reflectors disposed to simultaneously separate said illumination pattern of said colored image into three reflected illumination patterns, each in a different one of said plurality of discs having applicator surfaces separated from each other, and at least two rotatable screw-type toner application having screw applicator surfaces.

References Cited UNITED STATES PATENTS three primary colors, and a separate one of said line- 3O57720 10/1962 Hayford et a1 96-12 screens disposed in the path of each of said three re- 2O50417 8/1936 Bocca 95-122 flected illumination patterns 2365345 y 95 12'2 X 8. In apparatus for reproducing a colored image as de- 3313623 4/1967 Blxby 96-42 scribed in claim 7, wherein FOREIGN PATENTS means including additional dichroic reflectors are disposed in the paths of said three reflected illumination EZ SZ Q'IIIIIL 2 3;

patterns, after they have passed through said line screens, to superimpose said three illumination patterns on said recording element in superimposed register. 9. In apparatus for reproducing a colored image as described in claim 7, wherein each of said line screens comprises parallel opaque lines SAMUEL S. MATTHEWS, Primary Examiner R. P. GREINER, Assistant Examiner U.S. Cl. X.R. 

